Technical Field
The present disclosure relates to a power supply unit having a transformer.
Description of the Related Art
Generally, a power supply unit, such as a DC-DC converter, includes various electrical components, e.g. transformer, choke coil and others. These electrical components produce heat so that radiating heat produced thereby would be a problem when the power supply unit is shrunk or the power supply unit requires supplying large amount of current. For example, Japanese Patent No. 4924797 discloses a power supply unit in which a conductor of the secondary coil allowing a large amount of current to flow is fixed to a metal substrate fixed on a base plate. Hence, the power supply unit according to the above-described patent document achieves heat dissipation, that is, a heat produced by the secondary coil having relatively large heating value is effectively transmitted to the base plate via the metal substrate.
However, in the power supply unit according to the above-described patent document, an electrical component such as a rectifier is mounted in the vicinity of a connecting portion of the conductor at the secondary coil fixed to the metal substrate. Hence, in the vicinity of the connecting portion of the secondary coil, the temperature of the base plate and the metal-made plate are likely to increase so that it is difficult to radiate the heat produced at the secondary coil effectively. Similarly, heat dissipation from electrical components disposed near the same area is difficult to carry out.
Further, when the conductor of the secondary coil is connected to the base plate, the base plate itself produces heat due to current flowing in the base plate. As a result, it is difficult to radiate heat produced at the electrical components such as transformer or rectifiers.
Furthermore, electro-magnetic noise emitted from the transformer and the choke coil can be shielded in a base plate side. However, regarding the opposite side of the base plate, electro-magnetic noise is leaked externally if a shield plate is not provided so that the electro-magnetic noise is likely to influence the peripheral equipment. The electrical components that constitute the power supply unit are arranged on the base plate towards a direction where the base plate spreads. Therefore, the base plate becomes larger in the surface direction whereby the size of the power supply unit is likely to become larger.